Duracell batteries not registering full charge in BG-E4 battery grip.

[LocLocPhoto]

Hello.

 I suppose this is a heads up rather than a question.  I just purchased 2 new Duracell batteries for my 5D Mk 1 and noticed an issue.  When inserted in the Canon battery grip the new batteries only show 1 bar charge.  The old battery shows full charge in grip.  All batteries show full charge in the camera body without grip.  I’m an electronics service and repair tech so I checked batteries on a meter and they are all showing the the same voltage output.  Has anyone else encountered an issue using a grip?

[shadowsports]

Greetings ,

Unfortunately, Canon cannot control or guarantee 3rd party product compatibility.  You would have to ask the manufacturer (Duracell) about that.  Compatibility might vary by manufacturer.  

The 5D mkI is 19 years old.  I don't think you can still get original bp-511a batteries, so third party is probably your only option.  Another brand might perform differently.  It sounds like your 20-year-old camera has had a good life.  Maybe it's time to retire it and replace it with something more modern.